This invention relates to a heat shield arrangement with several tiles each being located on a wall and with at least one sealing element arranged between adjacent tiles, with the tiles being separated from the wall to form an interspace which can be supplied with cooling air.
The heat shield arrangement applies to a hot-gas conducting structure, in particular a metallic component of a gas turbine system or a gas turbine combustion chamber.
It is known from the state of the art that combustion chamber components, for example heat shields or tiles, are attached to the wall of a combustion chamber by a threaded connection without the use of sealing elements. Connection is accomplished by a bolt, with the rims of the tile directly abutting the wall of the combustion chamber. No sealing element is used in this type of connection.
Generally, these designs are disadvantageous in that the tiles rise from the wall of the combustion chamber under thermal load. The gap so formed allows cooling air to leak. Such leakage further increases the temperature of the tiles and, in turn, the gap at the tile rim. Ultimately, failure of the tiles or heat shields will occur.
From other designs, so-called strip seals are known. These strip seals are fitted into lateral slots between adjacent tiles or heat shields to seal them against each other. A design of this type is shown in Specification DE 10 003 728, for example. Here, seals of this type are provided as checkered plates which fit into corresponding lateral grooves in the tiles.
Clamp-type seals are known from Specification EP 1 130 219 A1 which engage grooves in the heat shield from the side opposite the hot gas. Here, the seal element can also be bellows-type or multi-part. Relative movement of the heat shields is ensured by the legs of the essentially U-shaped seals deforming during the operation of the gas turbine system.
The above seals, which are fitted into lateral slots, are disadvantageous in terms of assembly and cooling. The seals must be fitted into the slots after the tiles have been installed and must be secured against displacement. This process incurs high effort and may be technically critical, in particular where the accessibility of the sealing slots of individual tiles is restricted. These designs are further disadvantageous in that cooling air cannot adequately be supplied to the areas of the tiles which lie above the seals and their respective slots.
This applies in particular for seals according to EP 1 130 219 A1, where the area of two adjacent heat shields between the slots for the clamp-type seal cannot be supplied with air for the preferred method of effusion or transpiration cooling. In addition, the seal has a large radial extension and is, therefore, not flexible in the axial direction. Differences in thermal expansion along the tile edge due to temperature gradients or radial deformation for other reasons will compromise the quality of the seal.
A further problem dealt with in the present invention is that the conventional tiles are bolted rigidly to the wall of the combustion chamber. The bolt used here is normally a threaded bolt which is secured by a washer and nut. This rigid connection is associated with a significant increase of the mechanical stresses in the component. Under increasing temperatures, these stresses may easily exceed the permissible values, with cracks forming in the material of the wall of the combustion chamber.